Not Applicable
Not Applicable
1. Field of the Invention
This invention pertains generally to sterilization methods and, more particularly, to a method and apparatus for sterilizing organic and inorganic matter in a non-aqueous environment and for sterilizing air using a simultaneous combination of ultraviolet light wave energy and ultrasonic wave energy.
2. Description of the Background Art
The effective removal of viable pathogenic microorganisms is essential to those who regularly come into contact with potentially infectious microorganisms. Medical care givers, dentists and oral hygienists are frequently exposed to bodily fluids which may contain infectious microorganisms, such as viruses, bacteria, etc. Instrumentation (including human hands) must be effectively sterilized to prevent the transmission of potentially infectious microorganisms between patients and to the workers themselves. Microbiological researchers are constantly handling potentially infectious microorganisms as a regular part of their responsibilities and require effective and frequent sterilization of instrumentation and hands to protect themselves and their co-workers from such undesirable exposure.
People working in the field of food processing, packaging and service also have an essential need for the effective removal of potentially infectious microorganisms from a variety of food surfaces and the various equipment used in handling and processing. As part of their jobs, these workers are required to handle a variety of raw meats, poultry, seafood, baked goods, and vegetables for processing, packaging, delivery and sale to the general public. Food service workers are required to handle and prepare food products that are often to be consumed shortly thereafter by the public. Raw meats, poultry and seafood, especially, are ideal sources for the incubation and multiplication of undesired and potentially infectious microorganisms. A workers"" equipment and hands must be effectively sterilized on a frequent basis to prevent infecting themselves or spreading microorganisms from a contaminated source to the rest of the supply, and thus subjecting the general public to the risk of exposure.
Similarly, there is a need for effective removal of potentially infectious microorganisms from a variety of medical and dental instruments and devices that cannot be effectively sterilized by other conventional means such as autoclaving due to their internal electronic nature. These instruments and/or devices are often used on patients where infectious microorganisms that are present on the surface of the instruments and/or devices may be transmitted onto (or even into) the patient being treated if not effectively sterilized prior to its intended use, which can cause potentially life threatening conditions.
Food products available for public consumption also require effective removal of potentially dangerous microorganisms prior to consumption by the general public. As discussed above, handling of food products by workers with non-sterilized hands can result in the spread of undesired microorganisms, or conversely, direct contact of food products with contaminated food processing and packaging equipment can also result in the spread of unwanted microorganisms.
A commonly used method for sterilizing the hands of medical, dental and food service workers is repeated washing and/or scrubbing of the hands. This procedure. can be time consuming as it must be repeated frequently after the worker comes into contact with a potentially contaminated source. Also, this method may not effectively sterilize the worker""s hands due to ineffective washing techniques, type of cleaning agents used, or even the length of time spent physically cleaning the hands. Constant, repetitive hand washing can also damage the skin due to use of soaps, detergents and the actual scrubbing actions that remove the skin""s natural oils and can leave the skin dehydrated and irritated. The disadvantages of excessive time consumption, non-thorough hand sterilization, and skin irritation may cause the worker to avoid the frequent hand washing required to effectively prevent the spread of potentially infectious microorganisms.
Medical and dental instruments and devices are commonly sterilized via use of steam autoclaves and other methods that incorporate the use of heat, steam, gamma radiation, electron beam, and/or chemical agents to remove viable pathogenic microorganisms. However, the effectiveness of these methods varies and typically require the use of expensive, sophisticated equipment and generally involve a substantial amount of time to complete. Also, some instruments and devices are particularly sensitive to high temperatures, moisture, gamma radiation, electron beams and/or certain chemicals being used, and cannot survive these methods of sterilization. Therefore these instruments, in particular, require other methods of sterilization.
The use of ultraviolet light is another method used to sterilize organic and inorganic matter. Exposure to certain ultraviolet light band wavelengths has been discovered to be an effective means of destroying microorganisms. In using this method of sterilization, the user places the object or device to be cleaned into a chamber to expose the device or object to be cleaned to a prescribed dose of ultraviolet light. The interior of the cleaning chamber is usually coated with a reflective surface which reflects the light to ensure that all surfaces of the object being sterilized are irradiated with a sufficient amount of the ultraviolet light. The amount of time required for an adequate dosage of the ultraviolet light varies but typically requires at least ten seconds. However, the use of ultraviolet light for microbiological sterilization of organic and inorganic surface matter has historically been abandoned in favor of more sophisticated methods that employ heat, steam, gamma radiation, electron beams, and/or chemicals. This may be a result of manufacturers"" desire to offer more expensive sterilization devices in lieu of simplified technology. Typically, the use of ultraviolet light has been relegated to the treatment of air and/or water, which is generally circulated past the ultraviolet light source in a cabinet or the like and then into the sterilization environment.
Other sterilization methods involve the use of ultrasonic waves which resonate through an aqueous solution in which the item to be sterilized is immersed either partially or completely. The ultrasonic waves within the aqueous solution cause zones of compression and vacuity which act physically on the object placed within the aqueous solution causing foreign substances thereon to be dislodged and dispersed within the solution. When the object to be sterilized is a human hand, for example, the aqueous solution employed must be compatible with human skin, thus limiting the types of available aqueous solutions which can be used and are effective. Furthermore, because the hands have to be immersed into an aqueous solution to utilize this sterilization method, the hands become saturated with the aqueous solution and must thereafter be dried off. The hand drying process usually entails convecting air over the skin surface for a period of time until the hands are sufficiently dry. This consumes time and may even leave the skin dehydrated. If the item to be sterilized is some other organic material, such as meats, poultry, seafood or vegetables, immersing the item into an aqueous solution can damage or even destroy its properties, thus rendering the food product useless. Similarly, certain medical instruments and devices that need sterilizing become inoperable when they are immersed in an aqueous solution. These instances illustrate the need for a sterilization method which can effectively, frequently, and quickly sterilize organic and inorganic matter in a gaseous environment.
There are also sterilization methods which combine the use of both ultraviolet light and ultrasonic waves, however in all methods until the present invention, the ultrasonic emitting step has been performed in an aqueous solution. Using this method, an ultraviolet light source is positioned to irradiate a cleaning liquid in a cleaning tank into which the item to be sterilized is immersed. A piezoelectric transducer agitates the liquid ultrasonically causing both microscopic and macroscopic agitation, which dislodges foreign substances from the surface of the item. Because the ultraviolet irradiating step occurs concurrently with the ultrasonic process, the microorganisms dislodged from the item being sterilized are subjected to ultraviolet light, thereby destroying the microorganism. In these combination methods, the disadvantages associated with each step previously mentioned still exist.
The ability to sterilize environmental air or removing germs, bacteria and the like from air is also of value to healthcare workers, industrial sites and homes, among others. The reduction of transmission of diseases, including acquired immune deficiency syndrome, by airborne carriers is done using known air purification systems. This is usually done using air filters which must be replaced at periodic interval, either alone or in combination with germicidal levels of ultraviolet radiation and many methods have been developed using this approach. Filtration means are generally placed upstream of a number of ultraviolet lamps and air is passed near the lamps.
Therefore a need exists for a method and apparatus for sterilizing organic and inorganic material in a non-aqueous environment using a combination of ultraviolet light wave energy and ultrasonic wave energy. A further need exists for an increased efficiency method to sterilize air without the complexities and expenses of methods currently employed. The present invention satisfies those needs, as well as others, and overcomes the deficiencies in prior technology.
The present invention generally comprises a method and apparatus for sterilizing organic and inorganic materials using a combination of ultraviolet irradiation and ultrasonic emission. More particularly, the combination sterilization method of the present invention is performed in a non-aqueous environment. A typical example would be to sterilize the material while in the presence of a gas, such as air. In addition, the air itself can be sterilized. However, the material could also be sterilized in a vacuum, which those skilled in the art will appreciate is also a non-aqueous environment. It will be seen, therefore, that the invention departs from the known use of ultraviolet light and ultrasound for sterilization of materials in that the materials are not placed in a liquid, such as water, a chemical cleansing agent or the like, for sterilization. This does not mean, however, that the environment in which the materials are sterilized must be completely dehumidified in order to practice the present invention. In accordance with the invention, the materials to be sterilized are simply not immersed in a liquid. Thus the ultrasound emissions are applied in a non-aqueous environment such as air.
In accordance with an aspect of the invention, the ultraviolet light is emitted onto the surface of the material to be sterilized at wavelengths which will destroy viable pathogenic microorganisms. The material is subjected to a variable time duration sufficient to ensure complete destruction of microorganisms exposed to the ultraviolet light. During this period, the ultrasonic waves cause excitation and oscillation three-dimensionally on all exposed surfaces of the material, thereby causing microorganisms attached but not molecularly bonded to the surface of the material to become dislodged and momentarily airborne. As a result of being dislodged, the microorganisms experience a greater surface area exposure to the ultraviolet light energy than would otherwise be exposed if the microorganism were still attached to the surface of the material. The ultraviolet irradiating and ultrasonic excitation steps occur simultaneously to produce the desired effect of increased sterilization efficiency. Upon sufficient exposure time to the combined energy sources, the object is then removed from the chamber in a sterilized condition.
In accordance with another aspect of the invention, the combined use of ultraviolet light and ultrasound can be applied to mass sterilization of items produced on assembly lines. Because this sterilization method is performed in a non-aqueous environment and, hence does not require immersing the materials in a liquid, the ultraviolet light source and ultrasonic emitter assembly can be placed along the path of a moving conveyor belt. Then, as the mass produced items move along the conveyor belt, they will be exposed to the ultraviolet light from the ultraviolet light source and ultrasonic waves from the ultrasonic emitter. The ultraviolet light irradiation step occurs simultaneously with the ultrasonic wave emission process, thus making only a single exposure event necessary to produce the desired sterilization effect. This can be done without even having to stop the conveyor belt and, after exposure, the items continue along their path on the conveyor belt in a sterilized condition.
In accordance with still another aspect of the invention, mass-produced food items such as meats, poultry, seafood and vegetables can be sterilized using this combination method without affecting the taste or texture of the food items being treated. The ability of the combination sterilization method to perform effective sterilization in a non-aqueous environment such as air eliminates the need to expose the food item to any liquid which might affect the texture and/or taste of the food item. And, since the ultraviolet light impinges only on the surface of the food item being sterilized, and not beneath the surface due to its poor penetrating capabilities, the light will not xe2x80x9ccookxe2x80x9d or alter the interior of the food item or otherwise affect its taste or texture. It will be appreciated, however, that lengthy ultraviolet light exposure times at high power levels could cause a change in the surface characteristics of the food item being sterilized.
It will be seen, therefore, that an object of the invention is to provide a quick, efficient and reliable method for effectively eliminating potentially infectious microorganisms from environmental air using a simultaneous combination of ultraviolet light and ultrasonic waves.
Another object of the invention is to provide a combination ultraviolet and ultrasonic sterilization method in which the sterilization is performed in a non-aqueous environment such as air, a gas, air mixed with a gas, or even a vacuum.
Another object of the invention is to provide a method of sterilization which is non-hazardous and safe for the user and those in close proximity to the user.
Another object of the invention is to provide a method of sterilization which can be easily implemented to sterilize mass produced items made on an assembly line.
Another object of the invention is to provide a method of sterilization which can sterilize food items without affecting the texture and/or taste of the food item.
Another object of the invention is to provide a method of sterilization which is simple to use and which does not require special training or procedures to implement.
Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.